Evolution by Natural Selection Change OVER TIME What is evolution by natural selection? Adaptations will spread throughout a population (species) if: It helps an organism GET FOOD It helps an organism AVOID PREDATION It helps an organism ATTRACT A MATE How does Natural Selection Work? Variations (DO NOT HELP YOU TO SURVIVE…JUST A DIFFERENCE AMONG ORGANISMS) exist in a population…in here we have different eye color…DOES EYE COLOR help you to: GET FOOD? AVOID PREDATION? ATTRACT A MATE? How does Natural Selection Work? Adaptations: THESE TRAITS DO HELP YOU TO SURVIVE, – Examples: A turtles shell Bright colors Rattle on a rattle snake Natural Selection is a Theory. What is a Theory? A theory is a well supported testable explanation of phenomena that have occurred in the natural world Some Common Theories Include: Gravity Evolution by natural Selection Darwin’s Observations He was fascinated at how WELL ADAPTED the animals were to the island! He noticed that many of the animals he saw on the island closely resembled the animals on the main land but were a BIT DIFFERENT! Natural Selection The Struggle for Existence…survival of the fittest (fit-ability to survive and reproduce result of adaptations)! Members of the same species compete for food, living space, and mates Those that are faster or better camouflaged, ect are more likely to survive…sometimes leading to new traits! Darwin’s Theory of Natural Selection 1. Organisms overproduce offspring 2. No 2 organisms are exactly alike (So when competition exists, some may win!) 3. The organism BEST ADAPTED to the new environmental pressure will SURVIVE to REPRODUCE (and pass on adaptation to offspring)! 4. In time…(millions of year)…the traits in a population will change (and may form new species).